Compact antenna

ABSTRACT

An antenna comprising two sub antennas each sub antenna comprising at least one radiating element is disclosed. The two sub antennas comprise an inner sub antenna and an outer sub antenna. The antenna comprises signal feed circuitry for supplying a first signal to the inner sub antenna and signal feed circuitry for supply a second signal to the outer sub antenna. The at least one radiating element of the outer sub antenna comprises at least one flexible radiating patch mounted on a flexible material arranged to wrap at least partially around at least a portion of the inner sub antenna.

FIELD OF THE INVENTION

The field of the invention relates to antenna and in particularpreferred embodiments to compact, quasi omnidirectional antenna with twosub antenna for radiating two different signals.

BACKGROUND

Configuring a multi-directional or quasi-omnidirectional antenna that isan antenna that seeks to radiate uniformly in all directions in oneplane, with two sub antenna such that two independent signals can beradiated, in for example a dual band scenario, is challenging. Theproblems to be addressed are how to configure the antenna such that itcan work simultaneously for both signals while:

-   -   not unduly impacting RF performances of each signal    -   not unduly increasing the overall width/profile of the antenna    -   not unduly increasing the overall length of the antenna.

Maintaining a compact antenna is important not only for visualconsiderations but also to allow it to withstand harsh conditions suchas wind, gust effects and vibrations.

An antenna with an increased gain is generally provided by increasingthe overall length of the antenna in order to feed several radiatingelements (patches/dipoles) in series. Where two sub antenna transmittingtwo different signals are to be used such as in a dual band operation,then for a better decoupling between the signals, the currentlypreferred architecture is presented in FIG. 1 (antenna 1 above antenna 2inside the same radome).

Although this configuration may provide 2 sub-antennas that are welldecoupled, the overall dual-band antenna length increases the risk ofstructural weakness and susceptibility to environmental conditions suchas wind and gust effects.

Another solution to reduce the global antenna length could be to placeantenna 1 next to antenna 2 as presented in FIG. 2. This solution hasthe drawbacks of an increased overall width and the added cost of asecond radome.

It would be desirable to provide a compact antenna operable to radiatetwo signals in multiple directions without each unduly affecting the RFperformance of the other.

SUMMARY

The first aspect of the present invention provides an antennacomprising:

-   -   two sub antennas, each sub antenna comprising at least one        radiating element, said two sub antennas comprising an inner sub        antenna and an outer sub antenna,    -   signal feed circuitry for supplying a first signal to said inner        sub antenna and signal feed circuitry for supply a second signal        to said outer sub antenna,    -   wherein said at least one radiating element of said outer sub        antenna comprises at least one flexible radiating patch mounted        on a flexible material arranged to wrap at least partially        around at least a portion of said inner sub antenna, and    -   wherein an input port to said signal feed circuitry of one sub        antenna is at a different longitudinal end of said antenna to an        input port to said signal feed circuitry of the other of said        two sub antennas.

The problems associated with providing an antenna that has two subantennas in a format that is compact such that visual pollution androbustness to harsh conditions such as strong winds are improved hasbeen addressed by providing the two sub antennas as nested sub antennasone being provided within the other. This is made possible by the outersub antenna being formed of one or more flexible radiating patchesmounted on a flexible material that is arranged to wrap at leastpartially around a least a portion of the other sub antenna.

The use of a flexible material for mounting the flexible radiating patchallows it to be wrapped into a curved hollow form such that it cansurround another sub antenna and provide outwardly facing radiatingelements allowing radiation to be emitted outwards from a surface atleast partially surrounding the other antenna. Furthermore, by suitableselection of the flexible material, one that is substantiallytransparent to radio frequencies emitted by the inner sub antenna can beselected such that a nested antenna with good performance is provided.In this way a compact antenna is provided by the use of one or morehollow radiating elements that are able to wrap around the one or moreradiating elements of another sub antenna.

A further way of reducing interference between the two sub antenna andany coupling between them is for the input port supplying the signalfeed to the two different sub antennas to be located at different endsof the antenna. In effect, one antenna is flipped around the horizontalaxis compared to the other antenna.

In some embodiments, said at least one flexible radiating patch isconfigured to wrap around at least 70% of an outer circumference of saidinner antenna and in some embodiments around at least 80 or at least95%.

Having a radiating patch that wraps almost fully around the innerantenna provides a sub antenna that is effective in radiating insubstantially all directions in one plane and is in effect aquasi-omnidirectional sub antenna.

In some embodiments, said signal feed circuitry for each of saidantennas comprises: signal supply circuitry running in a substantiallylongitudinal direction parallel to an axis of said antenna from a signalinput; and at least one signal feed probe configured to capacitivelycouple said signal from said signal supply circuitry to a correspondingone of said at least one radiating patch.

In some embodiments, said signal feed circuitry for said outer antennacomprises conductive tracks mounted on said flexible material.

The signal feed circuitry for supplying the signal to the differentradiating patches may be formed by a substantial longitudinal trackrunning along the flexible material. This signal feed circuitry can be acause of coupling between signals and as such limiting it to onelongitudinal direction such that it can be appropriately shielded from,or arranged at a different circumferential position to, signal feedcircuitry of the other sub antenna may reduce this coupling and beadvantageous.

In some embodiments, said inner and outer sub antenna are arranged suchthat they are rotated about said longitudinal axis with respect to eachother, such that said signal supply circuitry of each sub antenna are atdifferent circumferential position and do not overlap.

As noted previously the signal supply circuitry may be a source ofinterference and coupling between the different antennas and where it isarranged along a longitudinal axis then it may be advantageous if thesub antenna are in effect rotated with respect to each other such thatthe signal supply circuitry are at different circumferential positionsand do not overlap, i.e. they are not located on a common radius.

In some embodiments, said flexible material of said outer sub antennacomprises a conductive patch mounted on an inner surface of saidflexible material, and said signal supply circuitry is mounted on anouter surface of said flexible material overlapping said conductivepatch.

In order to provide a ground plate for the signal supply circuitry andalso to shield it from the inner sub antenna to some degree a conductivepatch may be mounted on an inner surface of the flexible material. Theconductive patch may extend across a portion of the circumference of theflexible material and along a portion of its length.

In some embodiments, said at least one radiating element of said innersub antenna comprises at least one flexible radiating patch mounted on aflexible material, said flexible material being arranged such that anouter perimeter of a cross section of said inner sub antenna comprises acurved surface.

Although the inner antenna may have a number of forms, in someembodiments it too is formed from at least one flexible radiating patchmounted on a flexible material to form a curved surface. This fitsneatly within the curved surface of the outer antenna and also mayprovide an effective omnidirectional or quasi-omnidirectional subantenna.

In some embodiments, said inner sub antenna has substantially the samearchitecture as said outer sub antenna and said flexible material ofsaid inner sub antenna comprises a conductive patch mounted on an innersurface of said flexible material, and said signal feed circuitry forsaid sub antenna is mounted on an outer surface of said flexiblematerial above said conductive patch.

Although the inner antenna may have a different form to the outer subantenna in some embodiments it has substantially the same form albeitphysically smaller. In such an arrangement the conductive tracks formingthe feed supply circuitry will be offset with respect to each other byrotation of one sub antenna with respect to the other.

In other embodiments, said antenna comprises: a longitudinal conductivesupport member for supporting at least some components of said antenna;said signal feed circuitry for supplying a signal to said inner subantenna comprising signal supply circuitry mounted on an outer surfaceof said inner longitudinal support member and configured to supply saidsignal to at least one signal feed probe configured to capacitivelysupply said signal to said at least one radiating element of said innersub antenna; wherein said at least one radiating element comprises atleast one radiating patch mounted on a flexible material said flexiblematerial being mounted to at least partially wraparound saidlongitudinal support member.

An alternative arrangement for the inner sub antenna is to have a curvedradiating patch as the radiating element of the inner sub antenna but tomount this and the signal supply circuitry on a longitudinal conductivesupport member which acts both as a ground plane for the signal supplycircuitry and as a central support for the whole antenna providing itwith robustness and helping in problems arising due to harsh weatherconditions.

In some embodiments, each sub antenna comprises a plurality of radiatingelements arranged subsequent to each other along a longitudinal axis.

Although, the antenna may comprise sub antennas each with a singleradiating element, in many embodiments they will have a plurality ofradiating elements. The antenna may have a modular form with the numberof radiating elements depending on the power and performancerequirements. As these increase then the elements of the antenna may beduplicated along its longitudinal lengths and a longer, higherperformance antenna is provided.

In some embodiments, said two sub antennas are arranged such that saidplurality of radiating elements of said two sub antennas are offsetalong said longitudinal axis with respect to each other.

As noted previously, coupling between the radiating elements of the subantenna is to be impeded where possible and one way of doing this is toarrange two sub antennas so that they are slightly offset with eachother such that the radiating elements in the form of the flexibleradiating patches are longitudinally offset with respect to each other.This helps reduce coupling between the two sub antennas and also may beadvantageous for the inner sub antenna where it is in effect radiatingthrough a gap between the radiating patches of the outer sub antenna.

In some embodiments, said antenna comprises a dual band antenna and saidradiating elements of said each of said two sub antennas are operable toradiate in a different one of said dual bands.

Although the antenna may comprise a multi band antenna with theradiating elements of each of the two sub antennas radiating in the samefrequency band but with a differently polarised signal, in someembodiments the two sub antennas operate in different frequency bandsand the antenna provides a dual band antenna. The nested arrangementsmay be particularly effective for dual band antenna as the two subantennas will naturally have a different size, one being within theother. A dual band antenna will have reduced interference between thesignals as they operate in different frequency bands. Differentpolarisations of the two frequency bands could also be used to reduceinterference further.

In some embodiments, the antenna further comprises at least one furthersub antenna mounted between said inner and said outer sub antenna.

Although embodiments are applicable to two sub antennas nested withineach other it should be clear to the skilled man that a plurality of subantennas could be arranged in this way, one within the other to providea particularly compact multiple frequency band or multiple band antenna.

In some embodiments, said antenna comprises a quasi-omnidirectionalantenna configured to radiate in substantially all directions in oneplane.

This configuration is particularly applicable to a quasi-omnidirectionalantenna which is configured to radiate substantially uniformly in alldirections. Such an antenna does not have reflective portions and as ofsuch lends itself well to this nested arrangement particularly wherehollow flexible radiating patches are used as the radiating element(s).

Further particular and preferred aspects are set out in the accompanyingindependent and dependent claims. Features of the dependent claims maybe combined with features of the independent claims as appropriate, andin combinations other than those explicitly set out in the claims.

Where an apparatus feature is described as being operable to provide afunction, it will be appreciated that this includes an apparatus featurewhich provides that function or which is adapted or configured toprovide that function.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described further, withreference to the accompanying drawings, in which:

FIG. 1 shows an antenna comprising sub antennas arranged one above theother according to the prior art;

FIG. 2 shows an antenna comprising two sub antennas arranged side byside according to the prior art;

FIG. 3 shows differences in length between a prior art antenna and oneaccording to an embodiment;

FIG. 4 shows schematically the flexible material forming the support forthe radiating patch;

FIG. 5 shows the flexible material with the ground conductive plate onit;

FIG. 6 shows the flexible material with the ground conductive plate andsignal feed circuitry on it;

FIG. 7 shows the flexible material with the radiating patches and signalfeeding network mounted on it;

FIG. 8 shows how the plurality of these components are wrapped to formone of the sub antenna;

FIG. 9 shows two corresponding sub antennas of a same formation but ofdifferent circumferences mounted one within the other;

FIG. 10 shows a different form of internal sub antenna;

FIGS. 11A and B shows an inner sub antenna inside an outer sub antennaswhere positions have been selected to reduce coupling between the twosub antennas;

FIGS. 12-18 show example performance data for such antenna;

FIGS. 19-21 show example radiation patterns for such antenna; and

FIG. 22 shows the difference in dimensions of an antenna according tothe prior art and one according to an embodiment.

DESCRIPTION OF THE EMBODIMENTS

Before discussing the embodiments in any more detail, first an overviewwill be provided.

Embodiments provide a compact antenna formed of sub antennas nested oneinside the other. In some embodiments, each sub antenna has radiatingelements with curved surfaces such that each emits omnidirectional orquasi omnidirectional radiation.

The inner and outer sub antennas may have the same form althoughdifferent physical sizes or the inner sub antenna may be formed around acentral conductive supporting member which may form the ground plane forthe signal supply circuitry of this sub antenna. In other embodimentsthe ground plane for the signal supply circuitry may be formed as abrass conductive layer on the internal surface of the flexible materialholding the flexible radiation patches. In order to reduce coupling andincrease isolation between the two sub antennas the two sub antennas canbe flipped with regard to each other on the three axes.

Thus, they can be rotated around the Z axis to a selected angle toreduce coupling between the signals, such that the two signal feedcircuitries are not aligned. They may be moved along the Z axis with aparticular shift to provide a longitudinal offset between the radiatingpatches and one of the sub antennas may be flipped with respect to theother about the Z axis such that the feed inputs are at different endsof the antenna.

Embodiments seek to create a compact, low length, high gain dual-bandquasi-omnidirectional antenna.

Instead of superimposing two omnidirectional sub antennas longitudinallyon top of each other, the idea is to have one omnidirectional subantenna placed inside the other (antenna 1 inside antenna 2). In thecontext of omnidirectional antennas, placing one sub antenna inside theother (concentric design) will increase the coupling between the 2 subantennas and decrease the RF performances ([S] parameters and radiationpatterns). To address these issues, the antenna 1 (the internal one) hasin some embodiments been:

-   -   flipped versus antenna 2 on the 3 axis (X,Y,Z).    -   rotated versus antenna 2 around the Z-axis with an optimized or        at least preferred angle.    -   moved along the Z-axis inside antenna 2 with an optimized or at        least preferred shift.

It is proposed in one embodiment that the radiating elements are wrappedaround the antenna structure, the antenna structure forming a centralsupport rod type structure. In some embodiments, the feeding network isalso proposed to be wrapped around the antenna structure.

Where the antenna is a dual band antenna, the inner sub antenna, antenna1 corresponds to the high band frequency range due to its smallerdimensions. The outer sub antenna, antenna 2 corresponds to the lowerband frequency range.

In some embodiments there may be further sub antenna wrapped around eachother, the outer antenna transmitting at lower band frequencies than theinner antenna.

In some embodiments the antenna may be a multi-band antenna with the twosub antenna transmitting in the same frequency band.

In some embodiments, each sub antenna may transmit with differentlypolarized signals.

This concentric design with a specific internal sub antennaconfiguration allows a significant reduction in length while keeping thesame antenna width when compared to similar antenna of the prior artwithout compromising on RF performance. FIG. 3 shows a comparisonbetween the sub antennas being mounted in a longitudinal arrangementsimilar to that of FIG. 1 and an arrangement according to an embodiment.The proposed design may also reduce the total number of handling andmounting parts and reduce the visual impact due to the length reduction.

The polarization of each sub antenna may be fixed to be horizontal orvertical depending on the azimuth angle or may vary according to theazimuth angle.

This design is described here for a concentric high gain dual-bandomnidirectional antenna, however the skilled person would understandthat it could be extended to concentric multi-band omnidirectionalantennas where each sub antenna is configured to operate in the samefrequency band but is fed with different signals, these signals beingdifferently polarized to reduce coupling and interference between thesignals.

In this section, for a practical example, 2 concentric high gain quasiomnidirectional sub antennas will be described. The 2 sub antennas canradiate simultaneously with a high degree of signal isolation.

The 2 considered frequency bands are: [2.5 GHz-2.7 GHz] and [3.4 GHz-3.6GHz].

Antenna 1: the internal sub antenna designed for [3.4 GHz-3.6 GHz]frequency band.

Antenna 2: the external sub antenna designed for [2.5 GHz-2.7 GHz]frequency band.

Each sub antenna has its feeding network and radiating elements.

For both sub antennas the radiating elements are wrapped patchesoptimized according to each frequency band.

In this example, we consider that:

spacing between “antenna 1” patches=spacing between “antenna 2”patches=d=60 to mm.

d @ 2.7 GHz=0.54λ.

d @ 3.6 GHz=0.70λ.

The radiating elements are fed with equi amplitudes and equi phaserules.

The feeding network of antenna 1 is formed on a flexible material 1having a relative permittivity Dk1=2.25.

The feeding network of antenna 2 is formed on a flexible material 2having a relative permittivity Dk2=4.50.

External Sub Antenna Design—Antenna 2 (2.6 GHz Band):

Antenna 2 is composed of a cylindrical hollow pipe (flexible material)having 0.8 mm thickness (see FIG. 4).

A brass part is provided inside the cylindrical hollow pipe, as shown inFIG. 5, to form the ground plane of the feeding network.

The feeding part is composed of a T divider and capacitive couplingprobe printed on a flexible thin PCB sheet (0.05 mm). As shown in FIG.6, the feeding network is proposed to be wrapped on the upper face ofthe cylindrical pipe.

The radiating elements are wrapped cylindrical patches 30 using thinflexible PCB sheet (0.05 mm) rolled around the skeleton (see FIG. 7)provided by the hollow pipe formed of the flexible material. The hollowpipe 10 may have a cylindrical form, or the cross section may be someother curved form such as an ellipse. The antenna 2 can be viewed asbeing formed of one or more unitary cells each comprising a radiatingelement and feed network 20 (see FIG. 6). Where there are several ofthese they are arranged in series along the cylindrical hollow pipe asis shown in FIG. 7.

The unitary cell is duplicated according to the target gain to bereached (10 dBi peak gain). In our example, taking into account thelosses associated with the PCB that is used (Dk=4.5) and the spacingbetween patches (0.54 k), we have used 12 patches 30 for antenna 2 (seeFIG. 8) which we estimate should provide the target gain.

Internal Antenna Design—Antenna 1 (3.5 GHz Band):

The internal sub antenna (antenna 1) could be designed using 2 methods:

-   -   Method 1: The same design as antenna 2: both feeding network and        radiating elements are wrapped (see FIG. 9).    -   Method 2: An alternative design: (see FIG. 10).

In this design the internal antenna, antenna 1 comprises a centralU-shaped metallic rod 40 that provides support for many of the othercomponents of the internal sub antenna as well as providing a groundplane. Radiating patches 42 are wrapped around the central structurewhich comprises signal feed probe(s) for providing the signal to theradiating patch(es) 42. These signal feed probes are formed on a singlePCB which runs along the length of the antenna. Clips 48 are providedperiodically along the length of the signal feed probe PCB and theU-shaped metallic rod is held in position in U-shaped recesses withinthe clips.

A second PCB 46 is used as signal supply circuitry to supply a signal tothe signal feed probe(s) mounted on an outer surface of the U-shaped rodand locked in place by resilient closure members 44 which attach to theplastic clips. The closure member portion of the clip is slid inside thelower plastic part of the clip, and exerts pressure between the feedingPCB and the U shaped rod. As a result, grounding of the PCB is providedby the metallic rod 40 and the space available inside this U-shaped rodcan be used for the input signal cable where required.

Again the antenna 1 unitary cell is duplicated according to the targetgain to be reached (10 dBi peak gain). We have used 10 patches forantenna 1.

Antenna 1+Antenna2:

The antenna 1 position inside antenna 2 (FIGS. 11A and 11B) has beenselected to reduce couplings between the 2 antennas and improveomnidirectional patterns for each frequency band.

In this proposed solution, the antenna 1 (the internal one) has been:

-   -   flipped versus antenna 2 on the 3 axis (X,Y,Z).    -   rotated versus antenna 2 around Z-axis with an optimized angle.    -   moved along the Z-axis inside antenna 2 with an optimized shift.

The resulting dual band antenna has a length of 0.75 m with preliminarygood performances as set out in FIGS. 12 to 19.

FIG. 12 shows preliminary results of how the gain achieved in dB changeswith azimuth angle (phi) for antenna 2 operating at a frequency of 2.6GHz and with an elevation angle theta equal to 90°. It also shows anazimuth cut of the radiation pattern showing the omnidirectional natureof the antenna.

FIG. 13 shows similar results for antenna 1 operating at a frequency of3.5 GHz and with an elevation angle theta equal to 90°.

FIG. 14 shows an elevation section of the achieved gain (in dB) atdifferent azimuth angles of 0°, 45° and 90° for antenna 2, operating ata frequency of 2.6 GHz.

FIG. 15 shows an elevation section of the achieved gain (in dB) atdifferent azimuth angles 0°, 45° and 90° for antenna 1, operating at afrequency of 3.5 GHz.

FIG. 16 shows preliminary results for antenna 2 VSWR (voltage standingwave ratio), while FIG. 17 shows the same thing for antenna 1. In thisexample the Y axis is the VSWR and the flat line shows the specificationwhich in this case is 1.5.

FIG. 18 shows the isolation between the two signals from the two subantenna in dBs on the Y axis, while the flat line shows thespecification which in this case is −30 dB.

FIGS. 19-21 show the radiation pattern at azimuth and elevation anglesfor the antenna.

FIG. 19 shows the radiation pattern for the outer sub antenna, antenna 2while FIG. 20 shows it for the inner sub antenna, antenna 1. FIG. 21shows the radiation pattern for the inner sub antenna, antenna 1 withinthe structure of the antenna.

FIG. 22 shows the difference in dimensions and corresponding windloading between an antenna of the prior art and an antenna according toan embodiment with similar characteristics and performance.

It should be noted that in the context of this application a sub antennais an antenna, however, it is an antenna that is operable to radiate onesignal and is located within the same radome as another sub antenna thatis operable to radiate a different signal, the two sub antennas can beviewed as together forming an antenna.

It should be appreciated by those skilled in the art that any blockdiagrams herein represent conceptual views of illustrative circuitryembodying the principles of the invention. Similarly, it will beappreciated that any flow charts, flow diagrams, state transitiondiagrams, pseudo code, and the like represent various processes whichmay be substantially represented in computer readable medium and soexecuted by a computer or processor, whether or not such computer orprocessor is explicitly shown.

The description and drawings merely illustrate the principles of theinvention. It will thus be appreciated that those skilled in the artwill be able to devise various arrangements that, although notexplicitly described or shown herein, embody the principles of theinvention and are included within its spirit and scope. Furthermore, allexamples recited herein are principally intended expressly to be onlyfor pedagogical purposes to aid the reader in understanding theprinciples of the invention and the concepts contributed by theinventor(s) to furthering the art, and are to be construed as beingwithout limitation to such specifically recited examples and conditions.Moreover, all statements herein reciting principles, aspects, andembodiments of the invention, as well as specific examples thereof, areintended to encompass equivalents thereof.

1. An antenna comprising: two sub antennas, each sub antenna comprisingat least one radiating element, said two sub antennas comprising aninner sub antenna and an outer sub antenna, signal feed circuitry forsupplying a first signal to said inner sub antenna, and signal feedcircuitry for supply a second signal to said outer sub antenna, whereinsaid at least one radiating element of said outer sub antenna comprisesat least one flexible radiating patch mounted on a flexible materialarranged to wrap at least partially around at least a portion of saidinner sub antenna; and wherein an input port to said signal feedcircuitry of one sub antenna is at a different longitudinal end of saidantenna to an input port to said signal feed circuitry of the other ofsaid two sub antennas.
 2. An antenna according to claim 1, wherein saidat least one flexible radiating patch is configured to wrap around atleast 70% of an outer circumference of said inner antenna.
 3. An antennaaccording to claim 1, wherein said signal feed circuitry for each ofsaid antenna comprises: signal supply circuitry running in asubstantially longitudinal direction parallel to an axis of said antennafrom a signal input, and at least one signal feed probe configured tocapacitively couple said signal from said signal supply circuitry to acorresponding one of said at least one radiating patch.
 4. An antennaaccording to claim 3, wherein said signal feed circuitry for said outersub antenna comprises conductive tracks mounted on said flexiblematerial.
 5. An antenna according to claim 3, wherein said inner andouter sub antenna are arranged such that said signal supply circuitry ofeach sub antenna are at different circumferential positions and do notoverlap.
 6. An antenna according to claim 1, wherein said flexiblematerial of said outer sub antenna comprises a conductive patch mountedon an inner surface of said flexible material, and said signal supplycircuitry is mounted on an outer surface of said flexible materialoverlying said conductive patch.
 7. An antenna according to claim 1,wherein said at least one radiating element of said inner sub antennacomprises at least one flexible radiating patch mounted on a flexiblematerial, said flexible material being arranged such that an outerperimeter of a cross section of said inner sub antenna comprises acurved surface.
 8. An antenna according to claim 6, wherein said innersub antenna has substantially the same architecture as said outerantenna and said flexible material of said inner sub antenna comprises aconductive patch mounted on an inner surface of said flexible material,and said signal feed circuitry for said sub antenna is mounted on anouter surface of said flexible material overlying said conductive patch.9. An antenna according to claim 1, wherein said antenna comprises: alongitudinal conductive support member for supporting at least somecomponents of said antenna, said signal feed circuitry for supplying asignal to said inner sub antenna comprises signal supply circuitrymounted on an outer surface of said inner longitudinal support memberand configured to supply said signal to at least one signal feed probeconfigured to capacitively supply said signal to said at least oneradiating element of said inner sub antenna, wherein said at least oneradiating element comprises at least one radiating patch mounted on aflexible material, said flexible material being mounted to at leastpartially wraparound said longitudinal support member.
 10. An antennaaccording to claim 1, wherein each sub antenna comprises a plurality ofradiating elements arranged subsequent to each other along alongitudinal axis.
 11. An antenna according to claim 10, wherein saidtwo sub antennas are arranged such that said plurality of radiatingelements of said two sub antennas are offset along said longitudinalaxis with respect to each other.
 12. An antenna according to claim 1,wherein said antenna comprises a dual band antenna and said radiatingelements of said each of said two sub antennas are operable to radiatein a different one of said dual bands.
 13. An antenna according to claim1, comprising at least one further sub antenna mounted between saidinner and said outer sub antennas.
 14. An antenna according to claim 1,wherein said antenna comprises a quasi-omni directional antennaconfigured to radiate in all directions in one plane.